Performance of PRAME Immunohistochemistry in Distinguishing Classic Hodgkin Lymphoma from Anaplastic Large Cell Lymphoma and T-Cell Lymphoma.

BACKGROUND/OBJECTIVES: The differential diagnosis of classic Hodgkin lymphoma (CHL) versus anaplastic large cell lymphoma (ALCL) and other T-cell lymphomas (TCL) with Hodgkin-like features remains challenging in some cases, and may require TCR molecular testing with prolonged turnaround time. The limited literature has previously described PRAME (Preferentially Expressed Antigen in Melanoma) overexpression in Hodgkin cells and its absence in cutaneous T-cell lymphomas. The aim of this study was to examine the staining pattern of PRAME in CHL compared to the pattern in non-cutaneous ALCL and TCL. METHODS: Twenty-four cases of CHL, 21 cases of ALK-negative ALCL, nine cases of ALK-positive ALCL and 11 cases of other TCL were stained for PRAME. RESULTS: PRAME showed strong and diffuse (3+) expression in 80% of CHL cases while, in contrast, 0% of ALK-negative ALCL showed 3+ staining and 11% of ALK-positive ALCL showed 3+ staining. Non-ALCL TCL showed only 0 or 1+ staining. CONCLUSIONS: PRAME may be another helpful stain in the workup of CHL and its morphologic mimics.